Difference between revisions of "DUMPER tape format"
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| − | The original [[TENEX]] [[ | + | The original [[TENEX]] [[magnetic tape|tape]] [[backup]] program is called MINI-DUMPER or just DUMPER. It was written by Ray Tomlinson April 1971, in FAIL [[assembly language]]. The oldest version on record is from December 1971, and the newest is from February 1982. There is also a more elaborate program called BSYS, written at [[Stanford Research Institute|SRI]]. |
| − | (As a historical aside, the MINI-DUMPER user interface was considered atrocious which inspired making a command line library similar to the EXEC facility. This was later moved inside the [[TOPS-20]] monitor.) | + | (As a historical aside, the MINI-DUMPER [[user interface]] was considered atrocious which inspired making a [[command processor|command line]] [[subroutine package|library]] similar to the EXEC facility. This was later moved inside the [[TOPS-20]] [[monitor]].) |
| − | This was written primarily to document the reverse engineered MINI-DUMPER format. The format is an older version of what TOPS-20 DUMPER uses, and some information about the newer formats is included. | + | This was written primarily to document the reverse engineered MINI-DUMPER format. The format is an older version of what TOPS-20 DUMPER uses (below), and some information about the newer formats is included. |
===OVERVIEW=== | ===OVERVIEW=== | ||
| − | A DUMPER tape consists of a series of 518-word records, where the first six words is a header and the following 512 words are data. The first record is a tape header. After this | + | A DUMPER tape consists of a series of 518-word records, where the first six words is a [[header]] and the following 512 words are data. The first record is a tape header. After this comes [[file]]s, or optionally, [[directory]] data. A file is started by a file header record, followed by data records, and ended by a file trailer. The tape is terminated by a tape trailer. |
| − | DUMPER normally doesn't write any tape | + | DUMPER normally doesn't write any [[tape mark]]s except to terminate a saveset; marks are mostly ignored when read. MINI-DUMPER is much more particular about marks and requires them after tape headers and file trailers, and nowhere else. |
===TAPE FORMATS=== | ===TAPE FORMATS=== | ||
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===TAPE HEADER=== | ===TAPE HEADER=== | ||
| − | In format 0, the data is just an ASCIZ saveset name. | + | In format 0, the data is just an [[ASCIZ]] saveset name. |
If format 4, the data is: | If format 4, the data is: | ||
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|- | |- | ||
| 8 | | 8 | ||
| − | | Timestamp for saveset. | + | | [[Timestamp]] for saveset. |
|- | |- | ||
| 6+BFMSG | | 6+BFMSG | ||
| Line 129: | Line 129: | ||
In format 0, the only file header data is an ASCIZ string in the format DEV:<DIRECTORY>NAME.TYPE;VERSION;P123456;AUSER. | In format 0, the only file header data is an ASCIZ string in the format DEV:<DIRECTORY>NAME.TYPE;VERSION;P123456;AUSER. | ||
| − | Other formats have an FDB, file descriptor block at offset | + | Other formats have an FDB, file descriptor block at offset 0200 (octal) from the record header. |
===FILE TRAILER=== | ===FILE TRAILER=== | ||
| Line 138: | Line 138: | ||
These are optional in all formats. | These are optional in all formats. | ||
| + | |||
| + | ==External links== | ||
| + | |||
| + | * [http://bitsavers.org/pdf/dec/pdp10/Dumper_And_Backup_Tape_Formats_Oct82.pdf Dumper and Backup Tape Formats] - describes DUMPER format 4 | ||
| + | |||
| + | [[Category: PDP-10 Tape Formats]] | ||
Revision as of 11:50, 13 April 2022
The original TENEX tape backup program is called MINI-DUMPER or just DUMPER. It was written by Ray Tomlinson April 1971, in FAIL assembly language. The oldest version on record is from December 1971, and the newest is from February 1982. There is also a more elaborate program called BSYS, written at SRI.
(As a historical aside, the MINI-DUMPER user interface was considered atrocious which inspired making a command line library similar to the EXEC facility. This was later moved inside the TOPS-20 monitor.)
This was written primarily to document the reverse engineered MINI-DUMPER format. The format is an older version of what TOPS-20 DUMPER uses (below), and some information about the newer formats is included.
Contents
OVERVIEW
A DUMPER tape consists of a series of 518-word records, where the first six words is a header and the following 512 words are data. The first record is a tape header. After this comes files, or optionally, directory data. A file is started by a file header record, followed by data records, and ended by a file trailer. The tape is terminated by a tape trailer.
DUMPER normally doesn't write any tape marks except to terminate a saveset; marks are mostly ignored when read. MINI-DUMPER is much more particular about marks and requires them after tape headers and file trailers, and nowhere else.
TAPE FORMATS
There is a tape format number stored in the tape header. It more or less corresponds to the TOPS-20 release. MINI-DUMPER is retroactively assigned format number 0, and doesn't have the format number stored in the tape header.
| Format | Description |
| 0 | BBN original MINI-DUMPER format. |
| 3 | FDB changes, structures, "full dir spec". |
| 4 | New GTDIR blocks. Lowest legal format for latest DUMPER. |
| 5 | Encrypted passwords and other "CRDIR%iods". |
| 6 | "TONEXT" record type. |
RECORD HEADER
All records have a six-word header.
| Offset | Type | Description |
| 0 | Checksum | See below. |
| 1 | Access | Unused, set to 0. |
| 2 | Tape number | Starts from 1. |
| 3 | Page number | Starts from 0 in data pages; other records set to 0. |
| 4 | Record type | See below. |
| 5 | Sequence number | See below. |
The checksum is computed over all 518 words in the record, with the checksum set to 0. For formats 0-4, it's a one's complement sum. For format 5-6, it the sum is first rotated one step to the left and then adding in the data. The finished checksum is bitwise inversed before being stored in the header.
MINI-DUMPER expects the sequence number to start with 2, whereas later versions begin with 1. Normally each record increments the sequence number by 1, but a MINI-DUMPER tape header increments it by 2.
| Record Type | Number |
| Data | 0 |
| Tape header | 1 |
| File header | 2 |
| File trailer | 3 |
| Tape trailer | 4 |
| User directory | 5 |
DATA RECORD
TAPE HEADER
In format 0, the data is just an ASCIZ saveset name.
If format 4, the data is:
| Record offset | Description |
| 6 | Tape format number. |
| 7 | "BFMSG" - offset from header to start of saveset name? |
| 8 | Timestamp for saveset. |
| 6+BFMSG | Saveset name. |
FILE HEADER
In format 0, the only file header data is an ASCIZ string in the format DEV:<DIRECTORY>NAME.TYPE;VERSION;P123456;AUSER.
Other formats have an FDB, file descriptor block at offset 0200 (octal) from the record header.
FILE TRAILER
TAPE TRAILER
USER DIRECTORY
These are optional in all formats.
External links
- Dumper and Backup Tape Formats - describes DUMPER format 4
